anterior s's (sinus anterio´res) the anterior air cells that together with the middle and posterior air cells form the ethmoidal sinus.

aortic s's pouchlike dilatations at the root of the aorta, one opposite each semilunar cusp of the aortic valve, from which the coronary arteries originate.

carotid sinus a dilatation of the proximal portion of the internal carotid or distal portion of the common carotid artery, containing in its wall pressoreceptors that are stimulated by changes in blood pressure. See also carotid sinus syndrome.

cavernous sinus an irregularly shaped venous channel between the layers of dura mater of the brain, one on either side of the body of the sphenoid bone and communicating across the midline. Several cranial nerves course through this sinus.

cerebral sinus one of the ventricles of the brain.

cervical sinus a temporary depression in the neck of the embryo containing the branchial arches.

circular sinus the venous channel encircling the pituitary gland, formed by the two cavernous sinuses and the anterior and posterior intercavernous sinuses.

coccygeal sinus a sinus or fistula just over or close to the tip of the coccyx.

coronary sinus the dilated terminal portion of the great cardiac vein, receiving blood from other veins draining the heart muscle and emptying into the right atrium.

dermal sinus a congenital sinus tract extending from the surface of the body, between the bodies of two adjacent lumbar vertebrae, to the spinal canal.

ethmoid s's (ethmoidal s's) ethmoid cells.

frontal sinus one of the paired paranasal sinuses in the frontal bone, each communicating with the middle nasal meatus on the same side.

intercavernous s's channels connecting the two cavernous sinuses, one passing anterior and the other posterior to the stalk of the pituitary gland.

maxillary sinus one of the paired paranasal sinuses in the body of the maxilla on either side, opening into the middle nasal meatus on the same side.

occipital sinus a venous sinus between the layers of dura mater, passing upward along the midline of the cerebellum.

paranasal s's the eight cavities in the skull that are connected with the nasal cavity (see also Plates). They are arranged in four pairs, each of which has one member on the left and one on the right. The pairs are the maxillary sinuses in the maxillae; the frontal sinuses in the frontal bone; the sphenoid sinuses in the sphenoid bone behind the nasal cavity; and the ethmoid cells (ethmoid sinuses) in the ethmoid bone behind and below the frontal sinuses. The functions of the sinuses are not certain. They are believed to help the nose in circulating, warming, and moistening the air as it is inhaled, thereby lessening the shock of cold, dry air to the lungs. They also are thought to have a minor role as resonating chambers for the voice.

Sinus paranasal (Paranasal sinuses). From Dorland's, 2000.

petrosal sinus, inferior a venous channel arising from the cavernous sinus and draining into the internal jugular vein.

petrosal sinus, superior one arising from the cavernous sinus and draining into the transverse sinus of the dura mater.

transverse sinus of dura mater a large venous sinus on either side of the brain.

transverse sinus of pericardium a passage within the pericardial sac, behind the aorta and pulmonary trunk and in front of the left atrium and superior vena cava.

tympanic sinus a deep recess on the medial wall of the middle ear.

urogenital sinus an elongated sac that is formed by division of the cloaca in the early embryo, which ultimately forms most of the vestibule, urethra, and vagina in the female, and some of the urethra in the male.

uterine s's venous channels in the wall of the uterus in pregnancy.

uteroplacental s's blood spaces between the placenta and uterine sinuses.

sinus of venae cavae the posterior portion of the right atrium into which the inferior and the superior vena cava open; called also sinus venosus.

venous s's of dura mater large channels for venous blood forming an anastomosing system between the layers of the dura mater of the brain, receiving blood from the brain and draining into the veins of the scalp or deep veins at the base of the skull.

venous sinus of sclera a circular channel at the junction of the sclera and cornea, into which aqueous humor filters from the anterior chamber of the eye. Called also Schlemm's canal.

re·nal si·nus

[TA]

the cavity of the kidney, containing the calices and pelvis of the ureter and the segmental vessels embedded within a fatty matrix. The renal sinuses cause the kidneys to appear hollow or C-shaped on cross section or medical imaging.

re·nal si·nus

(rē'năl sī'nŭs) [TA]

The cavity of the kidney, containing the calyces and pelvis of the ureter and the segmental vessels embedded within a fatty matrix. The renal sinuses cause the kidneys to appear hollow or C-shaped on cross-section or medical imaging.

sinus

1. a recess, cavity, or channel, as (a) one in bone or (b) a dilated, valveless channel for venous blood.

2. an abnormal channel or fistula, permitting escape of pus. In common, unqualified usage, the word sinus refers to any of the cavities in the skull that are connected with the nasal cavity—the paranasal sinuses.

anal s's

furrows, with pouchlike recesses at their distal ends, separating the rectal columns; called also anal crypts.

basilar sinus

a dural venous sinus which runs on the floor of the cranial cavity and out through the foramen magnum.

cavernous sinus

an irregularly shaped venous channel between the layers of dura mater of the brain, one on either side of the body of the sphenoid bone and communicating across the midline. Several cranial nerves and, when present, the rete mirabile, course through this sinus.

cavernous sinus syndrome

lesions of the cavernous syndrome, caused by neoplasia or infectious agents, result in a dilated pupil and paralysis of the globe; vision is usually spared.

cerebral sinus

one of the ventricles of the brain.

cervical sinus

a temporary depression in the neck of the embryo containing the branchial arches.

circular sinus

the venous channel encircling the pituitary gland, formed by the two cavernous sinuses and the anterior and posterior intercavernous sinuses.

conchal sinus

cavity of the conchal bone.

coronary sinus

the terminal portion of the great cardiac vein, which lies in the cardiac sulcus between the left atrium and ventricle, and empties into the right atrium.

an air-filled recess in the head of birds which lies lateral to the nasal cavity into which it opens.

intercavernous sinus

channels connecting the two cavernous sinuses, one passing anterior and the other posterior to the stalk of the pituitary gland.

interdigitalis sinus

the cutaneous pouch, which lies between the claws of sheep and some other ruminants and whose wall contains apocrine glands, and whose duct surfaces on the skin just above the coronets; it serves as a trail gland.

lymphatic sinus

irregular, tortuous spaces within lymphoid tissues through which lymph flows.

maxillary sinus

one of the paired paranasal sinuses in the body of the maxilla on either side, opening into the middle meatus of the ipsilateral nasal cavity. In the horse it is divided into two compartments that communicate independently with the nasal chambers. All other sinuses of the horse communicate with the nasal chambers via the caudal maxillary sinus.

nasal sinus

see paranasal sinuses (below).

sinus nerve

a branch of the glossopharyngeal nerve; carries the afferent fibers of the stretch receptors in the wall of the carotid sinus.

a venous sinus between the layers of dura mater, passing along the midline of the cerebellum.

paranasal s's

mucosa-lined air cavities in bones of the skull, communicating with the nasal cavity and including ethmoidal, frontal, maxillary and sphenoidal sinuses.

petrosal sinus (inferior)

a venous channel arising from the cavernous sinus and draining into the internal jugular vein.

petrosal sinus (superior)

one arising from the cavernous sinus and draining into the transverse sinus of the dura mater.

prostatic sinus

the dorsolateral recess between the seminal colliculus and the wall of the urethra.

pulmonary trunk sinus

spaces between the wall of the pulmonary trunk and cusps of the pulmonary valve at its opening from the right ventricle.

red pulp sinus

vascular storage in the spleen into which capillaries empty.

sinus reflex arc

afferent fibers are in the sinus nerve; these connect with the cardioinhibitory and vasomotor centers which control blood pressure and heart rate via sympathetic fibers to blood vessels; provides a route for the sinus reflex which relates pressure in the carotid sinus to the performance of the circulatory system.

renal sinus

a recess in the substance of the kidney, occupied by the renal pelvis, calices, vessels, nerves and fat.

sagittal sinus (inferior)

a small venous sinus of the dura mater of large animals found between the cerebral hemispheres and opening into the straight sinus.

sagittal sinus (superior)

a venous sinus of the dura mater that courses between the cerebral hemispheres and ends in the confluence of sinuses.

a venous sinus of the dura mater on either side, continuous with the straight sinus and draining into the internal jugular vein of the same side.

sphenoidal sinus

one of the paired paranasal sinuses in the body of the sphenoid bone of some species. In the horse it communicates with the nasal cavity via the frontal and caudal maxillary sinuses.

sphenoparietal sinus

one of the venous sinuses of the dura mater, emptying into the cavernous sinus.

splenic sinus

dilated venous channels in the substance of the spleen. See also red pulp sinus (above).

straight sinus

a venous sinus of the dura mater formed by junction of the great cerebral vein and inferior sagittal sinus, and ending in the confluence of sinuses.

tarsal sinus

a space between the calcaneus and talus.

tentorial sinus

straight sinus.

transverse dura mater sinus

a large venous sinus that runs in the attached border of the cerebellar tentorium on either side of the skull.

transverse pericardial sinus

a passage within the pericardial sac, between the aorta and pulmonary trunk cranioventrally, and the left atrium and cranial vena cava dorsally.

tympanic sinus

a deep recess on the medial wall of the middle ear.

urachal sinus

an anomalous closure of the urachal canal in the newborn in which the opening at the umbilicus remains open. The bladder is normal. It is the cause of persistent infection and swelling at the umbilicus in the young animal and may lead to cystitis and pyelonephritis.

urethral s

a small cavity in the glans penis of the horse, above the urethral process; as a recess of the fossa glandis it is usually filled with a small mass (bean) of inspissated smegma.

urogenital sinus

an elongated sac formed by division of the cloaca in the early embryo, which ultimately forms most of the vestibule, urethra and vagina in the female, and some of the urethra in the male.

uterine sinus

venous channels in the wall of the uterus in pregnancy.

uteroplacental sinus

blood spaces between the placenta and uterine sinuses.

venae caval sinus

the posterior portion of the right atrium into which the inferior and the superior vena cava open.

sinus venarum

a chamber which is the greater part of the right atrium into which the great veins discharge.

venous sinus, sinus venosus

1. the common venous receptacle in the heart of the early embryo that receives blood from the umbilical and vitelline veins and from the body via the ducts of Cuvier.

2. sinus of venae cavae.

vertebral sinus

a continuation of part of the common occipital vein in birds; it emerges from the foramen magnum and accompanies the vertebral vein.

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